Acoustic enclosure comprising a non-heat-conducting external wall, an electrodynamic loudspeaker and an electronic control circuit

ABSTRACT

An acoustic enclosure ( 1 ), comprising:
         a non-heat-conducting external wall ( 20 ) at least partially defining a casing ( 25 ),   at least one electrodynamic loudspeaker ( 5 ) including a motor ( 48 ), the loudspeaker having a peripheral portion ( 50 ) fastened on the external wall, and   at least one electronic control circuit ( 10 ) of the loudspeaker.       

     The motor and the electronic circuit are connected to a same member ( 15 ) of the acoustic enclosure. The member conducts heat and includes an exchange surface ( 66 ) able to be traversed by a heat flow ( 68 ) circulating in the member originating from the motor and the electronic circuit when the acoustic enclosure is operating, the heat flow being intended to dissipate in the air ( 76 ) outside the acoustic enclosure or to pass into a heat-conducting element outside the acoustic enclosure.

The present invention relates to an acoustic enclosure, comprising:

-   -   a non-heat-conducting external wall at least partially defining        a casing of the acoustic enclosure,    -   at least one electrodynamic loudspeaker including a motor, the        loudspeaker having a peripheral portion fastened on the external        wall, and    -   at least one electronic control circuit of the loudspeaker.

Such a device is typically described as an “active acoustic enclosure”.In general, these elements are contained in a substantially airtightcasing with respect to the air outside the acoustic enclosure. Yet boththe electronic circuit and the loudspeaker(s) give off heat when theacoustic enclosure is operating. For example, the electric circuittypically gives off between 40 watts and 300 watts depending on theusage level. By using very high performing power supply andamplification technologies, the power given off is instead from 20 W to50 W.

The loudspeaker(s) typically give off up to 100 W of heat, for 1000 W ofelectricity received at its peak. Furthermore, the acoustic enclosure isgenerally used over a fairly long length of time.

There is thus a risk of overheating of the internal components of theenclosure due to heating of the inside air. The electronic circuit maybe damaged if the temperature of its components for example exceeds 65°C. Likewise, the spool of a loudspeaker may be damaged if itstemperature for example exceeds 200° C. Furthermore, the neodyme magnetsgenerally present in the motor of the loudspeaker may undergo apermanent loss of power if their temperature exceeds about 80° C.

To resolve these drawbacks, it is known to connect a heat sink to theelectronic circuit. The heat sink is placed inside the acousticenclosure. The heatsink ensures a rapid heat exchange between theelectronic circuit and the air inside the acoustic enclosure. Such asolution partially resolve the problem of heating of the electroniccircuit, but it is only appropriate for a relatively low-power acousticenclosure.

It is also known to use a heat sink placed outside the acousticenclosure and connected to the electronic circuit. This ensures coolingof the electronic circuit, but a risk remains of heating of theloudspeakers and the air inside the acoustic enclosure.

Likewise, it is known to fasten a radiator behind the loudspeaker, inthe casing of the acoustic enclosure. Such a solution does not make itpossible to dissipate a significant thermal power, and heating of theair inside the acoustic enclosure is observed.

It is also known to produce an acoustic enclosure whereof the externalwalls conduct heat. The external walls are for example made from metal.In general, these walls are thermally insulated from the loudspeakers bya seal providing acoustic sealing. The cooling time constants of theloudspeakers are high, approximately several hours.

Also known are so-called “bass reflex” acoustic enclosures, whichprovide an air exchange with the outside and therefore allow cooling ofthe inside air, in particular during strong movements of the membrane ofthe loudspeaker. It is known to place a heat sink of the electroniccircuit near the port, so as to maximize the heat exchanges with theoutside.

It is also known to protect the electronic circuit by using heat sensorsto limit the thermal power transmitted by the electronic circuit to theloudspeakers, or to stop the electronics or place them in standby untilthe electronic circuit has cooled to acceptable temperatures.

However, these technical solutions do not completely eliminate the riskof overheating, in particular during use of the acoustic enclosure atvery high power. These technologies lead to temporarily or permanentlylimiting the power of the acoustic enclosure.

One aim of the invention is therefore to provide an acoustic enclosureas described above and that is not limited, or is less limited, in termsof power due to the heating of its internal components.

To that end, the invention relates to an acoustic enclosure comprising:

-   -   a non-heat-conducting external wall at least partially defining        a casing of the acoustic enclosure,    -   at least one electrodynamic loudspeaker including a motor, the        loudspeaker having a peripheral portion fastened on the external        wall, and    -   at least one electronic control circuit of the loudspeaker,

wherein the motor of the loudspeaker and the electronic circuit areconnected to a same member of the acoustic enclosure, the memberconducting heat and including an exchange surface able to be traversedby a heat flow circulating in the member originating from the motor andthe electronic circuit when the acoustic enclosure is operating, theheat flow being intended to dissipate in the air outside the acousticenclosure or to pass into a heat-conducting element outside the acousticenclosure.

According to specific embodiments, the acoustic enclosure includes oneor more of the following features, considered alone or according to anytechnically possible combination(s):

-   -   the loudspeaker motor is fastened on the member directly or by        means of a chassis of the loudspeaker;    -   the motor of the loudspeaker or the electronic circuit is or are        connected to the member by at least one thermal bridge;    -   the member includes a radiator defining at least part of the        exchange surface, and a connecting portion, preferably made from        metal, to which the motor of the loudspeaker and the electronic        circuit are connected, the connecting portion being connected to        the radiator directly or via a thermal bridge;    -   the connecting portion is at least 80 wt % made from metal;    -   the connecting portion extends to the inside of the casing, in        particular through the casing;    -   the connecting portion is at least partially situated on the        surface of the acoustic enclosure so as to partially form the        casing;    -   the member inwardly defines at least one passage through the        acoustic enclosure, the passage including at least one inlet for        outside air, and an outlet, the passage being suitable for        allowing a circulation of outside air from the inlet toward the        outlet, and the member preferably comprising fins to favor a        dissipation of the heat flow in the outside air circulating in        the passage;    -   the acoustic enclosure comprises a fan to create a forced        circulation of outside air in the passage; and    -   the external wall is further fastened on the member, the        loudspeaker, the external wall and the member defining a        substantially airtight inner volume with respect to the outside        air.

The invention will be better understood upon reading the followingdescription, provided solely as an example and done in reference to theappended drawings, in which:

FIG. 1 is a sectional diagrammatic view of an acoustic enclosureaccording to a first embodiment of the invention,

FIG. 2 is a sectional diagrammatic view of an acoustic enclosureaccording to a second embodiment of the invention,

FIG. 3 is a diagrammatic view of the acoustic enclosure shown in FIG. 2,in sectional view along a plane substantially perpendicular to thesectional plane of FIG. 2, and

FIG. 4 is a sectional diagrammatic view of an acoustic enclosureaccording to a third embodiment of the invention.

In reference to FIG. 1, a loudspeaker enclosure 1 is described accordingto a first embodiment of the invention.

FIG. 1 is a sectional view along a plane P that is for examplehorizontal when the acoustic enclosure 1 is set on a horizontal surface(not shown) or fastened on a wall (not shown).

In the illustrated example, the acoustic enclosure 1 has a generallysubstantially parallelepiped shape. Alternatively, the acousticenclosure 1 has another general shape, advantageously substantiallyspherical.

The acoustic enclosure 1 comprises a loudspeaker 5, an electroniccontrol circuit 10 of the loudspeaker 5, a heat-conducting member 15,and a non-heat-conducting external wall 20 at least partially definingthe casing 25 of the acoustic enclosure.

The acoustic enclosure 1 further comprises a sealing gasket 30 insertedbetween the loudspeaker 5 and the external wall 20, a sealing gasket 32inserted between the external wall 20 and a first face 34 of the member15, and a sealing gasket 36 inserted between the external wall 20 and asecond face 38 of the member 15, opposite the first face 34 along atransverse direction T of the acoustic enclosure 1. The acousticenclosure 1 also comprises a first thermal bridge 40 connecting theloudspeaker 5 and the member 15, and a second thermal bridge 42connecting the electronic circuit 10 and the member 15.

The loudspeaker 5 comprises a chassis 44, a membrane 46, and a motor 48.The motor 48 is able to give off heat when the acoustic enclosure 1 isoperating. The motor 48 includes a spool defining an axis D of theloudspeaker 5 for example substantially parallel to the transversedirection T. The motor 48 is fastened on the member 15 via the firstthermal bridge 40.

“Thermal bridge” between two parts refers to one or several elementsconnecting the two parts and suitable for conducting heat in onedirection or the other between the two parts. For example, the elementsof the thermal bridge are suitable for the thermal resistance betweenthe two parts to be less than or equal to 5° C./W, preferably less thanor equal to 3° C./W, still more preferably less than or equal to 1°C./W. The main material making up the thermal bridge advantageously hasa thermal conductivity greater than or equal to 1 W/m·K.

According to alternatives (not shown), the chassis 44 or the motor 48are fastened directly on, or are in clean contact with, the member 15.

The chassis 44 includes a peripheral portion 50 relative to the axis Dand fastened on the external wall 20, advantageously over the entireperimeter of the loudspeaker 5 around the axis D.

For example, the membrane 46 is substantially planar, or substantiallyforms a sphere portion. The membrane 46 is suspended from the chassis44, advantageously by the sealing gasket 30.

The electronic circuit 10 for example comprises a printed circuit 52fastened on the second thermal bridge 42, and electronic components 54mounted on the printed circuit 52.

The printed circuit 52 is for example substantially parallel to aconnecting portion 56 of the member 15.

The electronic components 54 are able to give off heat when the acousticenclosure 1 is operating.

In the illustrated example, the member 15 extends inside and through thecasing 25, for example substantially perpendicular to the axis D of theloudspeaker 5. The member 15 comprises the connecting portion 56, aradiator 58 positioned in an opening 60 of the casing 25, and a thirdthermal bridge 62 connecting the connecting portion and the radiator.

According to alternatives (not shown), the third thermal bridge 62 isreplaced by a clean contact between the connecting portion 56 and theradiator 58, or by a paste or grease.

The connecting portion 56 for example has a generally planar shape. Theconnecting portion 56 is for example substantially perpendicular to theaxis D of the loudspeaker 5. The connecting portion 56 is for examplemade from metal, advantageously aluminum, magnesium or steel. Theconnecting portion 56 is for example a single piece.

According to one alternative that is not shown, the member 15 is made ina single piece.

The radiator 58 for example extends in a plane substantiallyperpendicular to the connecting portion 56. The radiator 58advantageously includes fins 64 protruding toward the outside of theacoustic enclosure 1. The radiator 58 defines an exchange surface 66able to be traversed by a heat flow 68 circulating in the member 15originating from the motor 48 and the electronic circuit 10 when theacoustic enclosure 1 is operating.

“Conductive” means that the member 15 has, at least over the journey ofthe heat flow 68, a conductivity λ greater than or equal to 1 W/m·K.

In the illustrated example, the external wall 20 comprises twohalf-shells 70, 72.

“Non-heat-conducting” or “thermally insulating” refers to a materialhaving a heat conductivity λ strictly less than 1 W/m·K.

The half-shell 70 is fastened on the peripheral portion 50 of theloudspeaker 5 and on the first face 34 of the member 15.

The half-shell 72 is fastened on the second face 38 of the member 15.

Owing to the sealing gaskets 30, 32, the loudspeaker 5, the member 15and the external wall 20 define a first substantially airtight innervolume 74 with respect to the outside air 76. The half-shell 72 and themember 15 define a second substantially airtight inner volume 78 withrespect to the outside air 76.

In the illustrated example, the first inner volume 74 houses the motor48. The second volume 78 houses the electronic circuit 10.

The operation of the acoustic enclosure 1 will now be described.

The member 15 places the motor 48, the electronic circuit 10 and theoutside air 76 in thermal communication.

When the acoustic enclosure 1 is operating, the motor 48 and theelectronic circuit 10 give off heat. In steady-state, the heat given offby the motor 48 passes in the member 15 via the first thermal bridge 40.The heat given off in the electronic circuit 10 passes in the member 15via the second thermal bridge 42. The heat flow 68 originating from themotor 48 and the electronic circuit 10 is created in the member 15. Theheat flow 10 traverses the third thermal bridge 62 and arrives in theradiator 58. The heat flow 10 then traverses the exchange surface 66 todissipate in the outside air 76.

Owing to the features described above, in particular the member 15, itis possible to extract a large fraction of the heat that is given off inthe motor 48 and in the electronic circuit 10, and to discharge itoutside the acoustic enclosure 1. It is thus possible to preventexcessive heating of the motor 48 or the electronic circuit 10.

Furthermore, at the beginning of use of the acoustic enclosure 1, theloudspeaker 5 is heated by the electronic circuit 10. Indeed, the heatgiven off by the electronic circuit 10 is conducted by the secondthermal bridge 42, the member 15 and the first thermal bridge 40 to themotor 48. The motor 48 gives off little or no heat as long as the soundvolume of the acoustic enclosure 1 remains low. Indeed, the powerconsumed ‘at rest’ by the electronic circuit is non-null, therefore fornull or low sound volumes, the majority of the heat production occurs atthe electronic circuit.

Furthermore, owing to the member 15, it is possible to make the casing25 from a material other than metal, while correctly discharging theheat given off by the motor 48 and the electronic circuit 10.

Advantageously, the member 15 constitutes an inner framework of theacoustic enclosure 1, on which the external wall 20 of substantiallytight material is fastened.

An acoustic enclosure 100 making up a second embodiment of the inventionwill now be described in reference to FIGS. 2 and 3.

The acoustic enclosure 100 is similar to the acoustic enclosure 1 shownin FIG. 1. In FIGS. 2 and 3, similar elements bear the same numericalreferences. Only the differences between the acoustic enclosure 100 andthe acoustic enclosure 1 will be described in detail below.

The acoustic enclosure 100 comprises a second loudspeaker 105, and asecond electronic circuit 110 for controlling the second loudspeaker105.

The second loudspeaker 105 is advantageously structurally similar to theloudspeaker 5. The second loudspeaker 105 in particular comprises amotor 148 able to give off heat when the acoustic enclosure 100 isoperating. The second loudspeaker 105 is for example positioned on theother side of the member 15 relative to the loudspeaker 5.

The motor 148 is connected to the member 15 by a fourth thermal bridge140.

The electronic circuit 10 is situated in the inner volume 74. Theelectronic circuit 10 is connected to the first face 34 of the member 15via the second thermal bridge 42.

The second electronic circuit 110 is situated in the second inner volume78. The second electronic circuit 110 is connected to the member 15 by afifth thermal bridge 142.

The fifth thermal bridge 142 is for example fastened on the second face38 of the member 15.

In the illustrated example, the member 15 occupies a substantiallymedian position in the casing 25 along the transverse direction T.

The first electronic circuit 10 and the second electronic circuit 110are for example connected by cables 112.

The member 15 of the acoustic enclosure 100 for example has no radiatorextending in an opening defined by the casing 25. The member 15 inwardlydefines a passage 114 through the acoustic enclosure 100.

As shown in FIG. 3, the passage 114 comprises at least one inlet 116 foroutside air 76, and an outlet 118. The passage 114 is suitable forallowing a circulation of outside air from the inlet 116 toward theoutlet 118.

The member 15 advantageously comprises fins 120 protruding in thepassage 114.

The circulation of outside air in the passage 114 is embodied in FIGS. 2and 3 by an arrow F.

The exchange surface 66 defined by the member 15 defines the passage114.

In a normal usage position of the acoustic enclosure 100, the inlet 116is situated below the outlet 118.

The passage 114 is suitable for working substantially as a chimney.

The operation of the acoustic enclosure 100 is similar to that of theacoustic enclosure 1, except that the heat flow 68 originating from themotor 48 and the electronic circuit 10 traverses the exchange surface 66to be carried by the air circulation F.

Likewise, a heat flow 168 originating from the motor 148 and the secondelectronic circuit 110 traverses the exchange surface 66 to pass intothe air circulation F.

According to an alternative that is not shown, the thermal dissipationmode of the acoustic enclosure 100 (chimney) and the thermal dissipationmode of the acoustic enclosure 1 (radiator) are combined.

Alternatively, the acoustic enclosure 100 comprises a fan (not shown)situated in the passage 114 and suitable for creating a forcedcirculation of outside air in the passage 144.

We will now describe an acoustic enclosure 200 making up a thirdembodiment of the invention.

The acoustic enclosure 200 is similar to the acoustic enclosure 1 shownin FIG. 1. Similar elements bear identical numerical references. Onlythe differences between the acoustic enclosure 200 and the acousticenclosure 1 shown in FIG. 1 will be described in detail below.

The member 15 comprises a connecting portion 156 situated on the surfaceof the acoustic enclosure 200 so as to partially form the casing 25.

The electronic circuit 10 is situated in the inner volume 74. The secondthermal bridge 42 is fastened on the first face 34 of the member 15.

The exchange surface 66 is defined by the radiator 58 and by the secondface 38 of the connecting part 156.

When the acoustic enclosure 200 is operating, part of the heat flow 68originating from the motor 48 and the electronic circuit 10 isdischarged in the outside air 76 via the second face 38 of the member15.

1. An acoustic enclosure comprising: a non-heat-conducting external wallat least partially defining a casing of the acoustic enclosure, at leastone electrodynamic loudspeaker including a motor, the loudspeaker havinga peripheral portion fastened on the external wall, and at least oneelectronic control circuit of the loudspeaker, wherein the motor of theloudspeaker and the electronic circuit are connected to a same member ofthe acoustic enclosure, the member conducting heat and including anexchange surface able to be traversed by a heat flow circulating in themember originating from the motor and the electronic circuit when theacoustic enclosure is operating, the heat flow being intended todissipate in the air outside the acoustic enclosure or to pass into aheat-conducting element outside the acoustic enclosure.
 2. The acousticenclosure according to claim 1, wherein the motor of the loudspeaker isfastened on the member directly or via a chassis of the loudspeaker. 3.The acoustic enclosure according to claim 1, wherein the motor of theloudspeaker or the electronic circuit is or are connected to the memberby at least one thermal bridge.
 4. The acoustic enclosure according toclaim 1, wherein the member includes a radiator defining at least partof the exchange surface, and a connecting portion to which the motor ofthe loudspeaker and the electronic circuit are connected, the connectingportion being connected to the radiator directly or via a thermalbridge.
 5. The acoustic enclosure according to claim 4, wherein theconnecting portion is at least 80 wt % made from metal.
 6. The acousticenclosure according to claim 4, wherein the connecting portion extendsinside the casing.
 7. The acoustic enclosure according to claim 4,wherein the connecting portion is situated at least partially on thesurface of the acoustic enclosure so as to partially form the casing. 8.The acoustic enclosure according to claim 1, wherein the member definesat least one passage through the acoustic enclosure, the passageincluding at least one inlet for outside air, and an outlet, the passagebeing suitable for allowing a circulation of outside air from the inlettoward the outlet.
 9. The acoustic enclosure according to claim 8,comprising a fan to create a forced circulation of outside air in thepassage.
 10. The acoustic enclosure according to claim 1, wherein theexternal wall is further fastened on the member, the loudspeaker, theexternal wall and the member defining an airtight inner volume withrespect to the outside air.
 11. The acoustic enclosure according toclaim 4, wherein the connecting portion is made from metal.
 12. Theacoustic enclosure according to claim 6, wherein the connecting portionextends through the casing.
 13. The acoustic enclosure according toclaim 8, wherein the member comprises fins to favor a dissipation of theheat flow in the outside air circulating in the passage.